A-Tech 16GB (4x4GB) RAM for Apple iMac (Mid 2010, Mid 2011, Late 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
iMac Core I7 Review (Mid 2010) - SlashGear
iMac 27" LCD Assembly, Mid 2010
Incase anyone ever needs the answer…I have a 27” 2010 iMac working in Target Display Mode with a M1 MacBook Pro using a miniDP to USB C adaptor that's capable of 4k60Hz.
Apple iMac 27-inch (July 2010) review: Apple iMac 27-inch (July 2010) - CNET